1. Field of the Invention
The present invention relates to methods and systems for measuring objects, and, more particularly, to a method and system for measuring an object by two image-capturing devices not disposed in parallel but configured to calculate three-dimensional coordinates of the object using a beam confluence collinear function.
2. Description of the Prior Art
Due to rapid technological evolution, automation systems, such as robots and robotic arms, play an increasingly important role in the operation procedures of product design, industrial manufacturing, and high-precision operation. Hence, it is imperative to optimize automation systems. The key to optimization of automation systems lies in precise identification of three-dimensional coordinates of an object by automation systems, such as robots and robotic arms. In view of this, there are different methods for measuring three-dimensional coordinates of an object.
U.S. Pat. No. 6,795,200 discloses a method for measuring dimensions of objects, comprising the steps of projecting structured light on a plane under test and capturing images of an object on the plane under test by two cameras disposed in parallel. This patent has at least two drawbacks. In practice, users incur extra costs in providing the structured light. And, calculation of three-dimensional coordinates of an object by simple trigonometric geometric principles rarely takes account of errors arising from observation by a camera, and thus the calculated three-dimensional coordinates of the object are seldom precise. The imprecise calculated three-dimensional coordinates of the object bring about much greater errors in the follow-up operation of a system. Hence, U.S. Pat. No. 6,795,200 is not practical and is inapplicable to high-precision operation.
US20060088203 discloses a method for measuring an object, comprising the steps of mounting a plurality of fixed cameras, such as three, above a working area concurrently so as to capture three-dimensional images of an object within the working area and calculate three-dimensional coordinates of the object by simple trigonometric geometric principles. However, as disclosed in the application, the three fixed cameras mounted above the working area are pricey and inflexible in operation, not to mention that they prove useless in taking pictures of a hidden space and thus are inapplicable to high-precision operation.
WO2008076942 discloses a method for measuring an object, comprising the steps of: disposing a single video camera on a movable robotic arm for performing a plurality of multi-angle imaging operations on an object within a working area; and calculating three-dimensional coordinates of an object by simple trigonometric geometric principles. However, performing a plurality of multi-angle imaging operations on an object within a working area by a single video camera is time-consuming, cost-inefficient, and otherwise impractical. As with U.S. Pat. No. 6,795,200 and US20060088203, the three-dimensional coordinates of an object resulting from a follow-up calculation operation involving simple trigonometric geometric principles are plagued with relatively large errors and thus are not applicable to sophisticated operation.
In view of this, it is imperative to provide a method and system for measuring three-dimensional coordinates of an object conveniently, quickly, and precisely such that the method and system are applicable to sophisticated operation.